A 63% market share for rail on the Edinburgh to London route has no doubt forced the airlines down the cheap as chips route.

https://www.railtech.com/all/2023/07/03/edinburgh-london-route-shows-europe-the-way-for-modal-shift/?gdpr=accept

 

As they clearly state in that text, a poor comparison is being made.  Comparing radically different products, with the lowest possible cost of one of them compared to the highest possible cost of the other!

When I go to the online booking engines for the next few days ... and you will note I have only single fares here Edinburgh to Stansted.   As I write, the lowest cost single airline flight southward is 10th January 2025 at £14.99    Edit to add with luggage to add £29.98 or £39.48 (single) for "essentials" or "standard plus". If you don't someehere from £6.40 to £18.99 so select a seat (yes, there is a skip button).  There are four days available in the following week for you to return at the £14.99 fare.

 

No-one is suggesting otherwise, and it's not about long distance rail travel - for clarity, and perhaps for those who haven't fully read the article, here is the summary of the findings, verbatim;

Research by Scottish Labour found a return flight from Edinburgh to London Stansted could cost as little as £29.98 - less than the £31.40 price of a peak-time ScotRail ticket between Glasgow and Edinburgh. The party also said it was either the same price or cheaper to book one-way flights to locations such as Dublin and Belfast than it was to buy a one-way peak fare from Edinburgh to Glasgow.

 
Airline flight prices are not "regulated" off-peak returns on long-distance rail routes such as the Edinburgh - London are "regulated"

By Regulated the DfT set the fare

 

The article is specifically drawing a comparison between peak time rail fares and flights, not off peak.

 
Just done a little on-line research.

National Rail enquiries gives an off-peak return standard class train fare from any Edinburgh station to any Glasgow station as £16-20. To get a cheap day return on the tram from Edinburgh city centre zone to the airport (seems the best deal) is £9-50, and cheapest Stanstead - Liverpool Street rail fare off-peak is £26-70.

Cheapest flights all seem to be to Stanstead or Luton, leaving at or before 7 am or after 18-45 from Edinburgh airport (so you've got to get there first and check in - say an hour earlier)

So - £16-20 by train Edinburgh - Glasgow, at least £66-18 by plane/train/tram Edinburgh - London, plus inconvenience of a very early start or getting there after business hours so needing overnight accommodation as well if you take an afternoon/evening flight.

That tram begins to look expensive!

 

London Stansted Parkway 

 
Also, is the flight fare a peak time last minute fare? Probably not.

 
City centre to city centres though?! Apples and pears

 
...........variation on the "plane cheaper than train" theme, but perhaps the most extreme one yet?

https://www.msn.com/en-gb/travel/news/edinburgh-to-london-flights-cheaper-than-train-to-glasgow-as-calls-made-for-reduction/ar-AA1wcQp9?ocid=socialshare